Electromechanical switch for use as a crosspoint for conversation circuits



June 8, 1965 A. J. HENQUET ETAL 3,188,425 ELECTROMECHANICAL SWITCH FORUSE AS A CROSSPOINT FOR CONVERSATION CIRCUITS Filed June 4, 1962lnuenlorg AJ HE/VQUE T E S lLEl-ZME By M/ A ttorn e y 3,188,425LECTROMECHANICAL SWITCH FOR USE AS A CRQSSPOINT FOR CONVERSATIGNCIRCUHTS Andr Jean Henquet and Fernand Silerme, Boulogne- Billancourt,France, assignors to International Standard Electric Corporation, NewYork, N.Y., a corporation of Delaware Filed June 4, 1962, Ser. No.199,916 Claims priority, application France, June 14, 1961, 864,957,Patent 1,299,665 4 Claims. (Cl. 200-87) The present invention relates toan electromagnetic switch, and particularly to a memory suitable for useas switch crossp'oints controlled by electronic circuits in telephone orother systems.

Semi-conductors have not yet fulfilled the various requirements presentin telephone switching systems, and more particularly in the crosspoints placed in the conversation circuits. On the other hand,electromagnetic relays are not suitable for crosspoint usage as theoperation time thereof is relatively long, and the memory function hasto be added thereto through means such as locking contacts and circuits.One object of this invention is to provide a switch which may be definedas a magnetic memory relay and may be controlled by relatively shortpulses the duration of which is of the order of microseconds rather thanon the order of milliseconds as is common for conventional relays. Theduration of the mechanical movement of such a relay caused by themagnetic flux could be longer than the pulse which sets said magneticflux.

Magnetic switches are known which utilize magnetic cores wherein theflux may be reversed by a pulse for producing the remanent fluxes whichset the switch in either position. In a switch of this type, ferritecores carrying windings have been combined in such a way that whenopposite fluxes were established in the cores, the resultant flux setthe switching element in energized position, whereas when fluxes inseries were established in said cores, the switching element was movedto its manual unoperated position. In another known switch of this type,one of the cores was constituted by a permanent magnet, yet it was insuch a magnetic circuit that the fluxes in series were acting to set theswitching element in energized position were as the oppositeenergization would substantially suppress the flux.

Another object of the present invention is to provide a switch of thefast acting electromagnetic type arranged to operate in equipment rackswithout mutual influence with the neighbouring magnetic relays orswitches.

According to a feature of the invention, the magnetic circuit of theswitch comprises a branch containing a permanent magnet which produces anearly constant flux,

. anotherbranch comprising a reversible magnet, preferably a metallicone (as opposed to ferrites), carrying a winding being able to reversethe flux thereof, and a branch comprising the switching element. Thelatter branch responds to the resultant flux when the reversible magnethas an opposite flux to the flux of permanent magnet to set theswitching element in the energized position. The branch structures aresuch that the fluxes of the two first branches do not substantially passover the third branch when they are in series, and this resets theswitching member in the position of rest. Preferably, a fourth branchmay be provided having a magnet keeper being able to control thereluctances of the three other branches.

According to another feature of the invention, the magnetic circuit isprovided with a magnetic casing constituted by a side which hugs thereversible magnet and constitutes the said magnet keeper, and twosleeves which surround the respective ends of said three branches of thecircuit.

United States. Patent Patented June 8, 1965 In a preferred embodiment,the envelope is constituted by a permeable magnetic material tube havinga portion cut out adjacent the permanent magnet and mobile magneticmembers of the said switch.

The switching member may be of the well-known magnetic reed contact typeenclosed in a glass tube. If necessary, one or several tubes may beprovided.

According to another feature of the present invention, the magnetic pathbetween said reed contacts and the other branches of the magneticcircuit is established without metallic or other magnetic contact, bymeans of pole pieces externally encompassing a large portion of the reedcontacts. This arrangement provides a sufficient magnetic permeancetogether with a complete electric insulation.

The above-mentioned and other features and objects of this inventionwill become more apparent by reference to the following descriptiontaken in conjunction with the accompanying drawing, in which:

FIGURE 1 represents the internal members of the switch, in elevation andin the relative position they have in the switch,

FIGURE 2 represents in perspective a magnetic yoke,

FIGURE 3 represents in elevation the members of FIG- URE 1 together withtwo magnetic yokes placed in position,

FIGURE 4 represents in elevation the above mentioned members enclosed inthe magnetic envelope,

FIGURES 5 and 6 represent a front view and a plane View or" the switchof FIGURE 4.

The switching member is constituted by two switching elements 1 (onlyone being shown in the elevation view of FIGURE 1) of a known typewherein two magnetic reeds 2, 3 are enclosed in a glass tube 4 in orderto constitute an electrical contact when their adjacent ends areattracted by a magnetic flux flowing through said reeds. The over-alllength of these elements may be mm.

On one side of these tubes is placed a permanent magnet 5. This magnetmust have a relatively high coercive force so that its magnetic fluxwill not be substantially modified during switch operations. An alloyknown by the trade name Ticonal (containing 8 to 35% of titanium, 15 to30% of cobalt, 10 to 25% of nickel and about 5% of aluminum) may beprovided. This alloy has a coercive field of 800 oersteds and a remanentinduction of 10,000 gauss. Magnet 5 may have a length of 25 mm. and asection of 20 mm. so that it has a coercive force of 2,000 oersteds anda remanent flux of about 2,000 M. An alloy known by the trade nameAlnico, for instance, may be also utilized, such alloy containing about6% of ti taniurn, 12% of cobalt, 15 to 30% of nickel and 8 to 10% ofaluminium, the remainder being iron. This alloy has a coercive field ofabout 500 oersteds and a remanent induction of about 7,000 G.

On the other side of the tubes, opposite magnet 5, a small bar 6 ispositioned which constitutes a reversible magnet carrying a magnetizingcoil 7. This small bar has also a high permeability, but a much lowercoercive force, and a substantially rectangular hysteresis loop. Thematerial in this bar 6 could be heat treated iron at high content ofchromium and carbon with an addition of silicon. The alloy utilized mayhave a coercive field of 70 to 80 oersteds and a remanent induction of9,500 gauss. The length of the small bar may be 62 mm., the section 28mm. so that the coercive force will be about 460 oersteds and theremanent flux about 2,600 M.

The three branches of the magnetic circuit constituted by the abovementioned members are magnetically coupled by two yokes 3, one of whichis shown in FIGURE 2, the other members and their yokes being shown inPEGURE 3. Yoke 8 comprises bush 9 enclosing the extremity of small bar 6and two bushes It enclosing tubes 4. These bushes are linked by blades11, the whole structure being formed by punching and bending a permeablemagnetic material sheet, for instance ductile iron. It will be notedthat the yokes are not in contact with the magnetic reeds 2, and thus donot need to be electrically insulated therefrom. Bushes which constitutepole pieces are relatively long so as to give a large surface to the airgap between them and reeds 2 to enhance the passage of the magneticflux. The utilization of small bars 5 and 6 having a great coerciveforce and a large remanent flux, insures the correct operation of theswitch under these conditions. Magnet 5 tangentially contacts bushes 10,but its main magnetic circuit will be completed by the outer envelope.

Envelope 12, shown in FIGURE 4 encompasses coil 7 and two bushes 14. Anaperture is cut out in the middle of envelope 12. Lugs 16 formed nearthe edges of this aperture may be welded to the extremities of permanentmagnet 5, so that flux from the magnet passes through the magnetic shuntconstituted by bushes 1d and side 13. As represented in FIGURE '6,bushes 1% surround inner yokes 940 with a certain space, so that themagnetic shunt also afforded by the envelope to bar 6 comprises a largeair gap. The space between bushes 14 and yokes 8 contains insulatingplugs 17 (FIGURE 5) for housing the electrical connections of theswitching reeds and the winding of coil 7.

In operation, the switch may have two energized states and twocorresponding remanent states. When the switch is in the de-energizedremanent state, the magnetization of bar 6 is in a reverse position withrespect to that of permanent magnet 5 (FIGURE 1), results in theirmagnetic fluxes being linked in series aided by yokes 8. Taking intoaccount the magnetic shunt afforded by envelope 12, a very small fluxpasses through reeds 2, and the switches remain unoperated. At themoment when an operating pulse is applied to Winding 7, themagnetization of bar 6 is reversed. If the pulse is a shoit one, the 7is applied bar 6 will resume its original magnetization and y will keepit after the termination of the pulse. The fluxes, in series, will avoidreeds 2-3 the easier as an air gap is left between them and yokes 8. Thereeds will move aside and will open the electrical contacts.

The establishment of the magnetic circuit according to the invention,with its members having a high permeability and a high coercive force inspite of their small size, its air gap and its magnetic shunt, ensures areliable operation, the conservation of the permanent magnet, a goodinsulation of the conducting reeds together with an economicconstruction and a fairly reduced size,

While the principles of the invention have been described in connectionwith a specific embodiment, it is to he clearly understood that thisdescription is made only by way of example and not as a limitation onthe scope of the invention. a

We claim:

1. An electromechanical switch for use as a crosspoint comprising: atleast one set of magnetic reed contacts; means including a permanentmagnet of relatively high coercive force for providing a substantiallyconstant flux within operating limits of said reed contacts; anelectromagnetic device having a core made of material with a lowcoerciveforce, high permeability and a square hysteresis loop; means forreversing the direction of magnetization of said core responsive toelectrical pulses of short duration; magnetic circuit means couplingsaid inagnet and said core for carrying substantially no flux when themagnet and core flux are in series aiding and for carrying a high level.of flux when the magnet and core flux are in series opposing; and yokemeans for completing said magnetic circuit; said yoke means having threebranch means, a first of said branch means providing an air gapsurrounding one of said contacts, a second branch means providing an airgap surrounding another of said contacts, and a third of said branchmeans receiving and holding said core.

2. The switch of claim 11 wherein each of said sets of contacts issealed in a glass tube, and said first and second branch means surroundand hold said glass tube, said air gap being the space between theinside of the glass tube and said contacts.

3. The switch of claim 2 and a magnetic envelope enclosing at least aportion of said magnetic reed contacts, there being a magnetic contactbetween said permanent magnet and said envelope, said envelope providingmag netic shielding for said switch.

4. The switch of claim 3 wherein said magnetic envelope comprises a sidepassing along said core and terminating at either end in a magneticbrush, saidbrushes surrounding said yoke without touching said yoke,said brushes also surrounding and forming an opening intermediate theends of said envelope, said contacts and said permanent magnet beingadjacent said opening.

References Cited by the Examiner UNITED STATES PATENTS 2,902,55s 9/59Peek 200- s7 2,938,982 5/60 Brown et al. 2004,? 3,002,066 9/61Ketchledge et al. 200-s7 3,008,019 11/61 Scheidig 200-87 3,056,868 10/62Jacobson et al. 200-87 3,061,696 10/62 Peek 200 s7 FOREIGN PATENTS617,984 4/61 Canada.

BERNARD A. GILHEANY, Primary Examiner. ROBERT SCHAEFER, Examiner.

1. AN ELECTROMECHANICAL SWITCH FOR USE AS A CROSSPOINT COMPRISING: ATLEAST ONE SET OF MAGNETIC REED CONTACTS; MEANS INCLUDING A PERMANENTMAGNET OF RELATIVE HIGH COERCIVE FORCE FOR PROVIDING A SUBSTANTIALLYCONSTANT FLUX WITHIN OPERATING LIMITS OF SAID REED CONTACTS; ANELECTROMAGNETIC DEVICE HAVI NG A CORE MADE OF MATERIAL WITH A LOWCOERCIVE FORCE, HIGH PERMEABILITY AND A SQUARE HYSTERESIS LOOP; MEANSFOR REVERSING THE DIRECTION OF MAGNETIZATION OF SAID CORE RESPONSIVE TOELECTRICAL PULSES OF SHORT DURATION; MAGNETIC CIRCUIT MEANS COUPLINGSAID MAGNET AND SAID CORE FOR CARRYING SUBSTANTIALLY NO FLUX WHEN THEMAGNET AND CORE FLUX ARE IN SERIES AIDING AND FOR CARRYING A HIGH LEVELOF FLUX WHEN THE MAGNET AND CORE FLUX ARE IN SERIES OPPOSING; AND YOKEMEANS FOR COMPLETING SAID MAGNETIC CIRCUIT; SAID YOKE MEANS HAVING THREEBRANCH MEANS, A FIRST OF SAID BRANCH MEANS PROVIDING AN AIR GAPSURROUNDING ONE OF SAID CONTACTS, A SECOND BRANCH MEANS PROVIDING AN AIRGAP SURROUNDING ANOTHER OF SAID CONTACTS, AND A THIRD OF SAID BRANCHMEANS RECEIVING AND HOLDING SAID CORE.